Ive come to the conclusion that trickle filters, wet/dry, are a problem with CO2 gas and the ability of the filter to do its job as well as it was designed to do.. from what I can tell if the wet/dry is hooked up to filter the water the way it is suppose to you can expect up to a four hundred percent loss in CO2.. I gathered this from reading what other people have posted about the consumption of CO2 in there system and how often they need to refill there compressed canisters. I dont think Ill be using a wet/dry in my planted tanks in the future.. thanks for the information guys.. its been great!!

I have a 75g Seaclear II with wet/dry trickle filter built-in to the back. When I first set it up in Dec 2004, I planted it and did fishless cycle - since then I have always measured 0 amm/0 nitrite/0 nitrate, doing about 5% water changes weekly. I have 160 W and have experimented with DIYCO2, up to 4X2L and trying different reactor methods, but have not seen any effect on plant growth with or without it (due to some secondary buffer in my tap water, I haven't been able to get confident measurements of CO2 concentration, but I doubt I've ever reached above ambient, which I at least partly blame to gas off from the trickle filter.) Surface agitation is very low. My vallisneria and water sprite have done great, rotala and crypts ok, but ambulia and wisteria have not done well.

I don't have any experience with cannister filters but I think any benefit you might get from the potentially higher biofilter capacity of a wet/dry filter would be redundant with the healthy plant growth of a high light, CO2 tank. So I think I would go with cannister for a high plant, CO2 injected system. One nice thing is my wet/dry filter needs essentially no maintenance - I rinse the pre-filter floss every once in a while when I feel like it, and that's about it.

Now, AFAIK many Mbunas will eat your plants, so along with the issue of higher pH (I guess you can acclimate them to a somewhat lower pH than natural, but I assume not too much), you may have a tough time growing a cool plant aquascape. I have not seen any heavily planted high light, CO2-injected East African cichlid tanks, but I'm sure there's someone out there doing it. So in your case, setting up a sump with wet/dry filter and planted refugium might be a really cool, innovative way to go. If you use floating plants and semi-aquatic pond plants, then CO2 won't be an issue.

I think the biggest problem with a wet/dry system would be with a DIYCO2 system.. the pressurized CO2 can just be cranked up, DIY is alot harder to get more CO2.. Mubas apparently eat plants that are native to Lake Malawi, ive heard they dive into some vals, but other than vals there are few native plants on the market.. I know there is a difference in bio-filtration between a wet/dry and a canister but I have never seen a scientific analysis of this difference. With a planted tank you need a nitrate factory after a while and both are nitrate factories after a while and again the difference, I dont know if that information is out there either..
czcz has a high light planted, planted refugium, reverse photoperiod, with DIYCO2 system if that interests you..

by the way you probibly need to start dosing for nitrate.. KNO3 is used for it, if you have a planted setup and have 0 nitrates, its one the nutrients that plants need.. most of people here try to keep it up in the 10-15ppm range.. actually you are suppose to start a nutrient regiment when nitrates reach 0.. you might need more help on this one.. you might want to do a search here on the forum for the regiments that have been listed by some of the members here..

I haven't seen any numbers on wet/dry vs. submerged biofilters, just lots of anecdotal info/people's experiences that many wet/dry methods (trickle bioballs, trickle floss, biowheel, etc) can filter a greater bioload than submerged media.

I've read a lot on using nutrient supplements, and I've been experimenting with KNO3 and Fe+trace fertilizers, but I have not seen any obvious benefit to plant growth (although I have not tried to hit a target NO3ppm level and may not have ever reached 10 ppm) and have not seen any obvious evidence of nutrient limitation such as yellow/transparent leaf tissue.

Right now, I'm pretty happy with my level of plant growth (not too much pruning required) and I'm more interested in having a natural-looking biotope tank than a Dutch-style luxuriant planted tank.